In recent years, mobile electronic equipment such as mobile-phones, game machines or the like has become popular and the quantities of secondary batteries installed therein have become larger and larger. Also, along with the development in wireless communication technology, there has been spreading of application of RFID (Radio Frequency Identification) which transmits & receives signals by very small power. In particular, it is possible for active RFID having power supply to achieve communication of several hundred meters or more. Thus, there are increasing hopes for application thereof to the health management of cows, horses or the like on farms, to the safety management of children when going to school and/or coming out of school, or the like.
On the other hand, for the sake of the maintenance and improvement of global environment, there have been actively carried out research and development of batteries having as little environmental loads as possible. Among those above, there has been broadly considered an idea that energy which is usually consumed unconsciously and also uselessly is converted to electric energy and used for charging, and this electric energy is utilized as power supply for mobile devices or the like.
In Patent Document 1, there is disclosed a vibration type electromagnetic generator which generates electricity by vibration applied from the outside.
FIG. 23 shows a constitution example of a vibration type electromagnetic generator 100.
The vibration type electromagnetic generator 100 is provided with a hollow pipe 105, two solenoid coils 104a, 104b wound around the pipe 105, and a movable magnet 101 which is movable inside the pipe 105. The movable magnet 101 is provided with two magnets 102a, 102b. The magnets 102a, 102b are joined through a spacer 103 made of a nonmagnetic body in a state in which the same magnetic poles thereof are faced to each other. When vibration is applied to the vibration type electromagnetic generator 100, the movable magnet 101 vibrates in a reciprocating manner in the winding axis direction of the solenoid coils 104a, 104b and electricity is generated.
It should be noted in the explanation below that there is also a case in which the solenoid coil is referred to as “coil” for short.